1. Field of the Invention
The present invention relates to a method for producing an optical recording medium having an organic dye layer and to an optical recording medium.
2. Description of the Related Art
That an organic dye such as a cyanine type, phthalocyanine type or azo type is used for recording layers of writable so-called recordable type optical recording media as represented by CD-R and DVD-R has been known.
In the formation of a recording layer which primarily contains an organic dye, generally such an organic dye as aforementioned is applied to a substrate by a spin coating method using an organic solvent such as cyclohexane, cyclohexanone, methanol, ethanol, isopropyl alcohol, diacetone alcohol, methyl cellosolve, ethyl cellosolve, butyl acetate or fluorinated alcohols singly or as a mixture. Then a reflecting layer is formed on the formed recording layer.
Meanwhile, it is demanded of optical recording media to have weatherability taking various working conditions into consideration. It is assumed to be desirable that a solvent is contained in a recording layer in a smaller amount to improve this weatherability. So a process is generally used in which an organic dye is dissolved in a suitable solvent to form an organic dye layer by a spin coating method and thereafter the residual solvent in the organic dye layer is dried in a proper drying step using high temperature drying, vacuum drying, air blast drying or the like, followed by forming a reflecting layer on the organic dye layer.
For example, Japanese Examined Patent Publication No. 7-96333 discloses a process in which a dye is dissolved in a solvent containing a fluorinated alcohol to prepare an coating solution and thereafter the coating solution is applied to a substrate and dried to form a recording layer.
For example, Japanese Laid-open Patent Application No. 4-369577 discloses a process in which the amount of a solvent in a recording layer is decreased by carrying out intentional drying after the recording layer is formed, to thereby make a reflecting layer when the amount of the solvent contained in the applied recording layer is 10% by weight or less based on the recording layer.
However, the drying step after the recording layer is formed has the drawback that it requires a long period of time to dry a solvent sufficiently. Such a drying step is unacceptable from the productional point of view. It is difficult to adopt such a way that the drying temperature is raised to avoid such a drying step requiring long time if its influence on the applied organic dye, on the resin used for a substrate or on the mechanical accuracy of a substrate is taken into account.
Also, in Japanese Laid-open Patent Application No. 4-369577, the amount of a solvent in a recording layer of the resulting optical recording medium is nowhere considered though the amount of a solvent in the recording layer when the reflecting layer is formed is considered.